Apparatus for inserting bolts into concrete



` April 18, 1950 s, M, DUNN 2,504,311

APPARATUS FOR INSERTING BOLTS INTO CONCRETE Original Filed May 10, 19413 Sheets-Sheet 1 INVENTR: J ram-IENy M. DUN/u ATroRNEy; j

April 18, 1950 s. M. DUNN 2,504,311

APISARATUS FOR INSERTING BOLTS INTO CONCRETE Original Filed ay 10, 1941I 3 Sheets-Sheet 2 JNVENTOR; .STEPHEN M. DUNN ATT URNL' Y.

April 18, 1950 s. M. DUNN APPARATUS FOR INSERTIHG BOLTS INTO CONCRETEoriginal Filed may 1o. 1941 3 Sheets-Sheet 55 ATTOREY.

mOn. T m m PHEN M. DUNN Patented Apr. 18, 1950 UNITED .s'rA'rss PATENTortica l 2,504,241 l i l I APPARATUS FO BOLTS M0 stephen M. mma, LeAngerer, oeuf. original alleman my 1o, 1941, serial No.

ivided and this application Febru- A ary 4, 1946, Serial No'. 645,400

' 1o claim. (c1. 1 4'0 My invention relates primarily to the art oiembedding bolts, studs, or the like in concrete or similar substances,and more particularly to a method and apparatus for accomplishing thispurpose.

My invention is of particular utility in construction work, andaccordingly, will be described in connection therewith, although it isto be recognized that my apparatus, method, and article may' be used inother arts without departing from the spirit of my invention. This is adivision of my co-pending application, Serial No. 392,896, iiled May 10,1941. and issued as U. S. Letters Patent No. 2,400,878, on May 28,-1946.

In the concrete construction art, it is commonly desirable or necessaryto set bolts or studs formed' of steel or other material so that one endthereof is embedded in a. mass of solid concrete. Such embedded bolts orstuds are frequently used to provide means whereby other structures maybe joined or iastenedto such a concrete mass. For example, in thefabrication of concrete building structures it is frequently necessaryto provide extensive metal piping systems. such-as plumbing, which mustbe fastened in somemanner to the concrete walls of the structure. Thestandard practice is to partially embed a series of bolts or studsl inthe concrete walls so as to leavejjan end thereof projecting, to whichthe piping may be tied by conventional methods. Heretofore, theembedding of the bolts or studs has A`been accomplished by either of twomethods:

(a) bolts or studs are set in the forms in which the walls are'originally cast so as to actually cast the. studs into the walls; or (b)the walls are first formed complete-and then are drilled by conventionalmethods, as by a pneumatic drill, to holes to receive the studs whichare secure'rlin the holes by anchoring devices or by cementing, or both.These are the only two methods of accomplishing this result known in theart at the present time, and both methods have many markeddisadvantages. For example, it is extremely expensive to cast studsdirectly in the concrete as it is poured as special provision thereformust be made in the concrete forms, and. particularly in the casing ofvertical walls, it is very dliiicult to secure a good bond between theconcrete and the studs as voids tend to form below the studs as theconcrete is poured. Also, by this standard method errors in location orchanges in plans after completion of the pouring of the concretefrequently necessitate the insertion of additional studs, which mustthen be put in by the second conventional method, which causes delay inconstruction. The second method, similarly, is expensive as specialholes must be drilled in the concrete, and the studs must then beanchored and cemented inthe holes, which arelabor-consuming operationsrequiring additional material such fas special anchors and cement, whichalso increase the cost. By either prior art method', however, only arelatively weak bond can be formed between the studs and the concrete,which allows the studs to pull out of the concrete if large pullingstrains are impressed thereon. Thus, such prior art methods are not onlyexpensive. to perform but actually produce only a' relatively weak bondbetween-the studs and the concrete;

For the purpose of simplicityin this specification and claims, I shalldescribe my invention as being used inl connection with a mass ofaggregated material," which I hereby define as meaning aggregated orfired earthen materials having a-low modulus of elasticity and beingsubstantially non-ductile, such as, for example, ooncrete, cement,brick, clayrand thelike, to all of which my invention is applicable.

A primary object'of rnyinvention is to provide a method and apparatusfor embedding a stud in a mass of aggregated material which is moreeconomical to use than the prior art methods described above and whichformsa much stronger bond between the stud .and the aggregated materialthan such prior art methods. I intend to accomplish this by sheetingavstud directly into a mass oi aggregated material so as to rigidly xthe stud therein. I have foundthat such a method is very economicalandattains a result f much superior to the standard methods describedabove. For example, a -large number of pulling tests have been run onsand-blasted studs which were carefully tamped and cemented in drilledholes in concrete blocks, in accordance with conventional prior artmethods. It was found that all of such studs could be pulled from theconcrete by applying a pulling force thereto of 900 pounds per squareinch, or less, of Icircumferential area of the embedded portion of thestud. Similar pulling tests conductedby me on studs embedded in concreteby my method, as described hereinafter, have established that thepulling force required to pull such a stud is commonly over 3800 poundsper square inch oi` circumferential area of the embedded portion of thestud.

In `fact, by extensive tests on pulling studs hav ing a diameter ofone-quarterA inch and which had been embedded in concrete by my process,I have discovered that a bond may-be formed between the stud and theconcrete of such strength that the stud will break before the bondbetween the stud and the concrete will break; i. e., the bond betweenthe stud and the concrete is greater thanthe breaking strength of thestud.

My process and apparatus include the use of a gun of special design forfiring a stud into aggregated materials. I have found that it isimportant in the practice of my process to hold the -surface of theaggregated material in place while the bolt is shot thereinto, and Iprefer to accomplish this by holding the muzzle of my gun solidlyagainst the aggregated material when the gun is fired and until the studis embedded therein, and this is a feature of my invention. Toaccomplish this purpose, it is necessary to provide for the exhaust ofgases from the gun barrel, to assist in preventing recoil of the gunbarrel away from the surface of the aggregated material, and it isanother object of my invention to provide a gun capable of accomplishingthis result.

It is also important to provide such a gun in which the recoil of thegun resulting from ring the same is put on the breechblock thereof whichis allowed to recoil independently of the gun barrel, thus furtherreducing the possibility of recoil of the muzzle of the gun from thesurface of the concrete. and this is another object of the invention.

A further object of my invention is to provide such a gun having alocking mechanism which is so designed that the gun cannot be red unlessthe muzzle of the gun is in pressure engagement with a surface. Thisfeature of my gun insures that the desirable supporting pressure isapplied to the concrete while the gun is being fired.

Althoughin carrying out the method of my invention it is important toprovide a supporting pressure on the surface of the concrete surroundingthe area to be penetrated by the stud during Figure 10 is a longitudinalsectional view of an alternative form of gun muzzle for my invention.

Figure 11 is a sectional view illustrating the position of the parts atthe time when the firing pin is fully retracted.

Referring to the drawings, I show a gun I5 including a breechblockmember l5 to which is rigidly secured, as by an upper bolt I1 and alower bolt i8, a handle frame member I9 having a handle 20 at its' outerend. The breechblock member i6 is formed to provide a central chamber 22and an outer chamber 23. and having an opening 24 in one side thereof,as best shown in Figure 6. The central chamber 22 is provided with afirst wall 25 at one end thereof anda second wall 26 at the' other endthereof, the latter being provided with a cylindrical boss 28 projectinginto the central chamber.

A gun barrel 29 is provided with a head member 30 which is rotatablysupported on the lower bolt i8 which passes through an opening 3| formedin the head member. The opening 3|. is provided with a counterbore 32 inwhich is retained a relatively stlff compression spring 33 which engagesthe inner end of the counterbore and also the second wall26 of the-breechblock member l5 so as to normally hold the head member 30forwardly with considerable pressure against the first wall 25 and awayfrom the second wall 26, in the position shown in Figure 1. The gunbarrel 29 is provided with a bore 35, the inner end of which is providedwith a cartridge chamber 36, the inner penetration thereof, it issometimes difficult for an operator to hold a gun barrel against thesurface and perpendicular to the surface so as to supply the necessarysupporting pressure from the muzzle of the gun. It is therefore anotherobject of my invention to provide means for applying such supportingpressure to such a surface by the gun barrel without requiring the gunbarrel to be perpendicular to the surface.

` Other objects and advantages will appear from the followingdescription and from the drawings, which are for the purpose ofillustration only and in which: i Figure 1 is a longitudinal sectionalview of my gun loaded with my novel projectile.

Figure 2 is a view similar to Figure 1 but illustrating the position ofthe parts during ring oi' the gun.

Figure 3 is an enlarged cross-sectional view taken on the line 3-3 ofFigure l.

Figure 4 is an enlarged cross-sectional view taken on the line 4-4 ofFigure 1.

Figure 5 is a longitudinal fragmentary sectional view, considerablyenlarged. taken on the line `5-5 of Figure 1.

. Figure 6 is a cross-sectional view taken on the line 6-6 of Figure 2.

Figure '1 is a diagrammatic view illustrating the gun muzzle in positionfor ilring. Figure 8 is a diagrammatic view illustrating the projectileand the gun muzzle at the conclusion of firing.

Figure 9 is a diagrammatic view showing the bolt at the conclusion ofthe operation.

end thereof being chambered at 3l so as to receive the cylindrical boss28, as best shown in Figure 2. The outer end of the gun barrel 23 formsa muzzle 38, and the gun barrel is provided with radial ports 39 whichcommunicate between the bore 35 and the outer chamber 23 of thebreechblock member I6, the outer chamber in turn communicating throughthe opening 24 in the side thereof with the atmosphere so as to permitexhaust gases to discharge therethrough from the bore.

The handle frame member I9 is provided with -a vertical wall 4| having acentral opening 42 therein in which is held the outer end of a guidesleeve 43 having an inner end 44 of reduced diameter which makes a closeiit with the walls of an axial bore 45 formed through the second wall 26of the breechblock member I6. The inner end 44 of the guide sleeve 43 isprovided with a ring pin bore 45 through which extends a firing pin 4l.I'he ring pin 41 is supported in an actuating cup element 48 so as topermit restricted relative axial movement therebetween, the ring pinbeing provided with a ring point 43 and an inner head 50 which limitsrightward movement of the ring pin relative to the actuating cupelement, and an outer head 5i engaged b'y a ring pin return spring 52which is adapted to normally hold the firing pin relative to theactuating cup element 48 in the position shown in Figure l. Theactuating cup element 48 is adapted for sliding movement in the guidesleeve 43, being guided therein by a lug 56 (Fig. 4) formed on the topof the actuating cup element and confined in a longitudinal slot 53formed in the top of the guide sleeve 43. A compression spring 54 isprovided in the guide sleeve 43 and engages the outer face ofthe'actuating cup element 48 and a screw plug 55 threaded into the outerend of the guide sleeve. the compression spring 54 exerting asubstantial leftward force on the actuating cup element 48 so as toyieldabl;

retain it in the position shown in Figure 1. The inner end of the guidesleeve 43 is cut away to provide a transverse slot 61.

As best shown in Figures 3 and 4, against the outer face of the secondwall 28 of the breechblock member I8 is provided a vertically movableplate member 58 which is guided for vertical movement by guide screws 58which are threaded into the second Wall 28 of the breechblock member.The plate member 58 has a cut-away central portion 60 providing ahorizontal face 8| having a sernicircular opening 82 therein. The radiusof the semicircular opening 82 is less than the radius of the inner head50 formed on the firing pin 41, and, as best shown in Figure 1, when thevplate member 58 is in its lowermost position, the semicircular opening82 partially encircles the firing pin 41 and the inner head 50 engagesthe plate member to prevent the firing pin from moving to the left fromthe position shown in Figure 1. Consequently, the vertically movableplate mem'- ber 58 comprises a means for preventing actuation of thefiring pin 41, and, as will be understood by those skilled in the art,the plate member mustbe raised before the firing pin can be moved to theleft into firing relation. The plate member 58 is normally retained inits lowermost position, as shown in Figure 3, by a leaf spring 64 whichengages the top of the plate member and which is suitably secured to thebreechblock member I6 as by screws 65.

Locking means is provided to positively lock the plate member 58 in itslower position, as shown in Figures 1, 3, and 5, which includes a stud66 which is slidably mounted in an opening 61 formed in the second wall26 of the breechblock member and having an inner end 68 projecting,

into the central chamber 22 into the line of the head member 30, thestud having a head member 69 thereon adapted to engage an angled topsurface 10 formed on the plate member 58. The stud 66 is normally urgedtoward locking position by a compression spring 12, one end of whichengages the head member 69 and the other end of which engages a bracketelement 13 rigidly fixed to the handle frame member |9 as by screws 14,the compression spring 12 being centered by the outer end 15 of the stud68 and by a boss 16 formed on the bracket element 13.

As best shown in Figure 5, a rectangular opening 11 is provided in thevertical wall 4| and acts as a guide for a trigger bar 18 passingtherethrough, to the outer end of which is fixed a trig- A iscylindrical and is externally threaded so as to accommodate a nut ||0after the stud has been embedded in a surface, as best shown in Figure9.

In operation, the gun |5 is first loaded with the cartridge |00, theoperating parts of the gun being initially in the position shown inFigure 1. To accomplish this loading operation, the gun barrel 29 isfirst rotated on the lower bolt I8 in a counterclockwise direction, asseen in Figure 6, to the position -shown by dotted lines ||3 showntherein, rotation of the gun barrel being stopped by engagement thereofwith a shoulder |4 formed by one wall of the opening 24 in thebreechblock member I6. When the gun barrel 30 is in the position shownby the dotted lines ||3 of Fig. 6, it will be noted that the bore,indicated by dotted lines I5 thereof, is aligned with an arcuateopening-fl I6 formed in the breechblock member |6A through which thecartridge |00 may be inserted into the cartridge chamber 38 formed inthe gun barrel. The gun barrel is then rotated in aclockwise directionback to the full line position shown in Fig. 6, in which the gun isready for firing.

Prior to ring of the gun, the muzzle 38 of the gun barrel 29 is firmlypressed against the surface ||1 of the mass of aggregated material ||8into which the stud |04 is to be embedded. Force is then applied by theoperator through the handle 20 to move the handle frame member |9 andthe breechblock member I8 rigidly secured thereto to the left, as seenin Fig. 1, against the action of the compression spring 33 to cause thecylindrical boss 28 formed on the second wall 26 to move into thechambered portion 31 of the cartridge chamber 36 to the position thereofshown in Fig. 2. During such leftward movement of the ger handle 19, thetrigger bar 18 also being guided by passing through a rectangular slot80 formed in the bracket element 13, as best shown in Figure 4, therectangular slot 80 providing an engagement shoulder 8| at the topthereof for a purpose to be described hereinafter. The inner end of thetrigger bar 18 is provided with a vertical slot 82 in which is disposedan L-shaped releasing dog 83 having an upper leg 84 and a lower leg 85and being pivoted to the trigger bar by a suitable pivot pin 81 passingtherethrough. Resiliently engaging the lower leg 85 of the releasing dog83 is the free end of a leaf spring 88 suitably fixed to the trigger bar18, so as to tend to rotate the releasing dog in a clockwise directionas seen in Figure 1. Also secured inthe trigger bar 18 is a cross pin 89which engages beneath a spring plate 90, .the inner end 9| of which isinserted into a suitable slot 92 formed in the plate member 58, as besti breechlock member I6, as soon as the head member 30 of the gun barrel29 engages the inner end 68 of the stud 66, the stud 66 is moved totheright to the position shown in Fig. 2, in which the head member 89thereof is out of engagement with the angled top surface 10 of thevertically movable plateunember 58, permitting the top of the platemember to clear the head member 69. Since the semicircular opening 62 inthe plate member 58 normally encircles the firing pin 41 between theinner head 50 formed on the firing pin and the inner wall 26, it will beapparent that the firing pin cannot be moved to the left from theposition shown in Fig. l into engagement with the primer |02 of thecartridge |00 until the vertically movable plate member58 has beenraised to the position shown in Fig. 2. Consequently, it will beunderstood thatthe stud 66, which is normally held in the position shownin Fig. 1 by the compression spring 12, operates as a locking means toprevent firing of the gun i until such time as the muzzle 38 of the gunbarrel 29 is in strong pressure engagement with the surface ||1. This isan important featureof 'the invention.

With ihestud se in its unlocking position, as.

||8 of Fig. i to the position in which it is shown in Fig. 2. As thetrigger handle 18 and the trig' ger bar 18 move rearwardly from theposition shown in Fig. 1, the cross pin 88 secured in the trigger barmoves along beneath the spring plate 80 until it engages the cam face 85thereof. at which time it exerts a cam action on the spring plate whichlifts the same to the position thereof shown in Fig. 2. Since the innerend 8| of the spring plate 90 is secured in the vertically movable platemember 58, lifting of the spring plate 90 causes a similar lifting ofthe plate member 58 against the action of the leaf spring 04 to move theplate member upwardly to the position shown in Fig. 2, in which thehorizontal face 3| and the semicircular opening 82 of the plate memberare raised above the inner head 50 of the firing pin 41. As will also beappreciated, rightward movement of the trigger bar 18 causes a similarrightward movement of the actuating cup element 48, due to engagement ofthe lower leg 85 of the releasing dog 03 with the lug 50 formed on theactuating cup element, thus compressing the compression spring 54 andstoring energy therein. Upon continued movement of the trigger bar 18 tothe right, the upper leg 84 of the releasing dog 83 engages theengagement shoulder 8| (Fig. 2) formed on the bracket eiement 13, so asto cause the releasing dog to rotate in a counterclockwise direction soas to rotate the lower leg 85 thereof out of engagement with the lug 58formed on the actuating cup element 48. The stored energy of thecompression spring 54 is released thereby, which drives the actuatingcup element 48 and the firing pin 41 to the left at high speed. theactuating cup element 48 stopping its leftward movement upon engagementwith the guide sleeve 43, in the position shown in Fig. 2, but thefiring pin 41, due to its inertia, continues its leftward movement andthe point 49 thereof pierces the primer |02 of the cartridge case IOI tofire the cartridge in a manner well known in the art. Fig. 2 shows thefiring pin 41 having just pierced the primerv |02 to nre the cartridge|00, and shows the projectile |03 just starting its travel through thebore 35 of the gun barrel 29.

Under the impact of the explosion of the powder 39 the projectile |03travels outwardly through th bore 35 ofthe gun barrel 29- and enters them of material to approximately the position shown in Fig. 8.- It is tobe noted that until `after the projectile |03 has penetrated the mass ofaggregated material |I8 to its desired depth. the muzzle 38 of the gunbarrel '29 is held in pressure engagement with the surface |I1 of theaggregated material, thus providing substantial support for the surfaceof the aggregate material around the area of penetration of theprojectile |03. This is an important feature of nLv invention. Fromextensive tests, I have discovmuzzle 38 of the gun barrel 28 in pressureengagement with the surface I I1 of the mass of material ||8 during thetiring of the gun I5, several additional features are incorporated inthe gun. For example, during firing, after the projectile |03 has passedoutwardly through the bore 35 beyond the radial ports 39, the combustiongases from the powder 99ggmay then pass raered that unless the muzzle 38of the gun barrel 28, or some other equivalent support, is provided forthe surface ||1 of the mass of material III around the area ofpenetration of the projectile |03, the mass of material around such areainvariably cracks and shatters. and usually forms a small crater aroundthe embedded stud, which is very undesirable as it mars the surface I I1and weakens the bond between the projectile and the f Fig. 9.

dially outwardly therethrough to exhaust to the atmosphere, reducing thenatural recoil of the gun barrel 29 which would occur if these portswere omitted'. So long as the muzzle 38 of the gun barrel 29 is held inpressure engagement with the surface ||1 of the aggregated material I|8during firing of the gun I5, as described, the projectile |03 willcleanly enter into the mass of aggregated material without cracking,shattering, or otherwise marring the surface I I1 thereof.

After the projectile I 03 has been red into the mass of aggregatedmaterial IIS, as shown in Fig. 8, the cylindrical piston |05 may bereadily removed therefrom, as by cutting or otherwise, and a standardnut ||0 may be threaded onto the projecting end of the stud |04, asshown in Thus, the projecting portion |09 of the stud |04 may be used asa tie member for fastening any desired object to the mass of aggregatedmaterial I I8.

In Fig. 10 I show an alternative embodiment of the invention, whichprovides means for insuring a solid supporting pressure against thesurface ofthe supporting material around the area to be penetrated bythe stud. In this form of the device, a gun barrel |20 is provided for agun (not shown) which is in all respects similar to the gun I5 exceptfor the muzzle construction 'to be described. The outer end of the gunbarrel |20 is machined to provide a spherically convex muzzle |2|adapted to fit against a spherically concave surface |22 formed in afoot member |23 having a at engaging end |24 adapted to engage thesurface |25 of a mass of aggregated material |26. The foot member |23 isprovided with an axial bore |21 of considerably larger diameter than thebore |28 of the gun barrel |20, and is provided with radial exhaustports |28 which communicate between the axial bore |21 and theatmosphere to permit the exhaust of air ahead ofthe projectile when itis fired. The foot member |23 is yieldably held in engagement with themuzzle |2| by a tension spring |30, one end of which is bent into asuitable tapped opening I8| in the gun barrel |20 and the other end ofwhich is bent into a suitable tapped opening |32 in the foot member, oneend portion of the spring being retained in a helical groove |33 cut inthe periphery of the gun barrel and the other end portion of the springbeing retained in a helical groove |34 cut in the periphery of the footmem-I ber. It will thus be apparent that the gun barrel |20 may deviateseveral degrees in any direcytion from the perpendicular to the surface|25 without unseating any portion of the engaging end |24 from thesurface |25 of the mass of aggregated material |26. This feature of theinvention obviates the necessity of holding the gun e barrel |20 exactlyperpendicular to the surface support for the surface ||1 directlysurrounding the area of penetration of the projectile |03.

|25, as must be done with the gun barrel 28. while retaining an evensupporting pressure around the area to be penetrated by the stud. Theradial exhaust ports |28 also permit the release of air ahead of theprojectile when it is fired, which further reduces the tendency of thegun barrel to recoil from the surface |25 during To additionally assistin maintaining the u firing ofthegun.

Although I have shown and described a preferred embodiment of myinvention, it will be understood that certain parts and elements thereofmay be replaced by mechanical equivalents without departing from thespirit of my invention. Consequently, I do not intend to be limited tothe specific embodiment shown and described, but desire to be affordedthe full scope of the following claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

l. A gun for shooting attachment projectiles into substances so as tohave them embedded therein comprising means providing a gun barrel, achamber to receive a cartridge and said projectile, means for firing thecartridge, and a foot member attached to and having the axis thereofshiftable relative to the axis of the gun barrel so as to be capable ofbeing positioned squarely against the surface of the substance to bepenetrated independently of the degree of deviation of the body of thegun barrel from a position normal to said surface.

2. A gun for shooting attachment devices into substances so as to havethem embedded therein comprising means providing a gun barrel, a chamberto receive said attachment device and means for propelling saidattachment device through the gun barrel, and a foot member attached toand having the axis thereof tiltable relative to the axis of the barrelwhereby said foot member is capable of being adjusted flatly against thesurface of the substance to be penetrated independently of the degree ofdeviation of the body of the gun barrel from a position normal to saidsurface.

3. A gun for shooting attachment devices into substances so as to havethem partially embedded therein comprising means providing a. gunbarrel. a chamber to receive said attachment device and means forpropelling said attachment device through the gun barrel, and anadjustable foot member having a flat outer face, said foot member andthe gun barrel having a ball and socket joint therebetween whereby thefoot member is capable of being adjusted flatly against the surface ofthe substance to be penetrated independently of the degree of deviationof the body of the gun barrel from a position normal to said containingthe projectile, means for firing the` cartridge, and an adjustable footmember having a ball and socket joint with the gun barrel and aresilient element attached to the foot member and the gun barrel wherebysaid foot member is capable of adjusting itself relatively to the bodyof the gun barrel so as to be capable of being positioned flatly againstthe surface of the substance to be penetrated independently of theposition of the body of the gun barrel and to return therefrom atcompletion of the discharge.

5. A gun for shooting projectiles into substances so as to have thempartially embedded therein comprising means providing a gun barreladapted to receive a cartridge, the muzzle end of said barrel beingequipped with a foot plate movably attached to the barrel, means forattaching the foot plate to the gun barrel so as to resist movement ofthe foot platelongitudinally of the gun barrel but permit lateralmovement of the foot plate with respect thereto, said foot plate havinga bore larger in vdiameter than`the bore of the barrel whereby the axisof the bore of the gun barrel may deviate considerably from a linenormal to theV engaging surface of the foot plate and the foot plate andthe gun will function as a unitary structure in providing an inert masseither held or pressed against the surface of the substance. f

6. A gun for shooting attachment projectiles into substances so as tohave them partially embedded therein comprising means providing ajointed gun barrel adapted to receive a cartridge containing theprojectile, means for firing the cartridge, said jointed barrelcomprising a fixed portion and a foot plate adjustably secured to thefixed portion and capable of adjusting itself relatively to the xedportion and to a position squarely against the surface of the substanceto be penetrated independently of the position of the body of the gunbarrel, there being outlets for air in the jointed gun barrel ahead ofthe projectile.

7. A gun for shooting attachment projectiles into substances so as tohave them partially embedded therein comprising means providing a gunbarrel adapted to receive a. cartridge containing the projectile, meansfor ring the cartridge, foot plate adjustably secured to the barrel`breechblock mounted around the barrel adapted for movement endwise withrespect thereto and spring means adapted to extend the barrel relativeto the breechblock, means for igniting the explosive charge, means onthe breechblock adapted to prevent the ignition of said charge until apositive pressure is applied to the end of the barrel against the springmeans, comprising an arresting device normally holding said ignitingmeans in inoperative position, and a release responsive to movement ofthe barrel relative to the breechblock for releasing said arrestingdevice.

9. A gun comprising a barrel having a bore therein open endwise to theatmosphere, a chamber to receive a projectile and an explosive charge,means for igniting said explosive charge, a breechblock mounted forspring-loaded longitudinal movement relative to the barrel, arrestingmeans on the breechblock for the firing pin, a pressure release thereforcooperable with the barrel adapted to prevent the ignition of saidcharge until a positive pressure is applied to the end of said barreladapted to move said barrel relative to the breechblock, and a series ofinterconnected passage means through the barrel communicating betweenthe chamber and the atmosphere adapted to permit the escape of air inthebarrel directly into the atmosphere ahead of said projectile.

l0. A gun comprising a stock, a barrel having a longitudinally movableattachment to the stock, a chamber in the barrel adapted to receive aprojectile and an explosive charge, a firing pin mechanism in the stockfor igniting said explosive 1l a charge, means to prevent the ilnitionof said charge until a positive longitudinal pressure is applied to theend of said barrel comprising pressure means adapted to normally extendthe barrel relative to the stock. an arresting device on the stocknormally engaging the mechanism in safety position, and a release forsaid arresting device responsive to movement of the barrel against thepressure means and actuable by longitudinal movement oi' the barrelrelative to the stock.

M. DUNN.

, iz nmnnnczs Crum UNrrnD STATES rATENTS Number Name Dete Miller Aug.23, 1921 Smith Sept. 4, 1923 Pipes June 23, 1936 Temple Apr. 6, 1943

